Plug-in Derived Cumulative into the Metric-Registry

[mayurkale22]

Fixes #450

Completed earlier PRs.

• Add support for Cumulative API
• Plug-in Cumulative APIs into the Metric-Registry
• Add support for Derived Cumulative API
• Plug-in Derived Cumulative APIs into the Metric-Registry (current)

[draffensperger]

Seems like some of this code is duplicated with other metric adding functions. That isn't necessarily bad but makes me wonder if there would be a more templatized approach to the different metric types. (On the other hand, Duplication is better than the wrong abstraction so I think this is fine)

[mayurkale22]

Ok, thanks.

[codecov-io]

Codecov Report

Merging #513 into master will increase coverage by 0.17%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #513      +/-   ##
==========================================
+ Coverage   94.78%   94.96%   +0.17%     
==========================================
  Files         147      147              
  Lines       10486    10780     +294     
  Branches      907      913       +6     
==========================================
+ Hits         9939    10237     +298     
+ Misses        547      543       -4

Impacted Files	Coverage Δ
src/trace/propagation/noop-propagation.ts	40% <0%> (-10%)	⬇️
src/common/noop-logger.ts	11.11% <0%> (-5.56%)	⬇️
src/stackdriver-monitoring.ts	80.89% <0%> (-1.13%)	⬇️
src/internal/string-utils.ts	100% <0%> (ø)	⬆️
test/test-tag-map.ts	100% <0%> (ø)	⬆️
src/resource-labels.ts	100% <0%> (ø)	⬆️
test/test-metric-producer-manager.ts	100% <0%> (ø)	⬆️
test/test-exporter-buffer.ts	100% <0%> (ø)	⬆️
test/test-metric-component.ts	100% <0%> (ø)	⬆️
test/test-sampler.ts	100% <0%> (ø)	⬆️
... and 30 more

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